1. Field of the Invention
The present invention relates to isolated polypeptides having xylanase activity and isolated polynucleotides encoding the polypeptides. The invention also relates to nucleic acid constructs, vectors, and host cells comprising the polynucleotides as well as methods for producing and using the polypeptides.
2. Description of the Related Art
Xylan, a major component of plant hemicellulose, is a polymer of D-xylose linked by beta-1,4-xylosidic bonds. Xylan can be degraded to xylose and xylo-oligomers by acid or enzymatic hydrolysis. Enzymatic hydrolysis of xylan produces free sugars without the by-products formed with acid (e.g., furans).
Enzymes capable of degrading xylan and other plant cell wall polysaccharides are important for the food industry, primarily for baking and in fruit and vegetable processing such as fruit juice production or wine making, where their ability to catalyse the degradation of the backbone or side chains of the plant cell wall polysaccharide is utilized (Visser et al., Xylans and Xylanases, Proceedings of an International Symposium, Wageningen, The Netherlands, Elsevier Science Publishers, 1992).
Other applications for xylanases are enzymatic breakdown of agricultural wastes for production of alcohol fuels, enzymatic treatment of animal feeds for hydrolysis of pentosans, manufacturing of dissolving pulps yielding cellulose, and bio-bleaching of wood pulp [Detroym R. W. In: Organic Chemicals from Biomass, (CRC Press, Boca Raton, Fla., 1981) 19-41; Paice and Jurasek, J. Wood Chem. Technol. 4: 187-198; Pommier and Fuentes, 1989, Tappi Journal 187-191; Senior et al., 1988, Biotechnol. Letters 10: 907-9121].
WO 92/17573 discloses a substantially pure xylanase derived from Humicola insolens and recombinant DNA encoding said xylanase for as a baking agent, a feed additive, and in the preparation of paper and pulp.
WO 92/01793 discloses a xylanase derived from Aspergillus tubigensis. It is mentioned, but not shown that related xylanases may be derived from other filamentous fungi, examples of which are Aspergillus, Disporotrichum, Penicillium, Neurospora, Fusarium and Trichoderma. The xylanases are stated to be useful in the preparation of bread or animal feed, in brewing and in reducing viscosity or improving filterability of cereal starch.
Shei et al., 1985, Biotech. and Bioeng. Vol. XXVII, pp. 533-538, and Fournier et al., 1985, Biotech. and Bioeng. Vol. XXVII, pp. 539-546, describe purification and characterization of endoxylanases isolated from Aspergillus niger. 
WO 91/19782 and EP 463 706 discloses xylanase derived from Aspergillus niger origin and the recombinant production thereof for use in baking, brewing, paper-making, and treatment of agricultural waste.
WO 03/012071 discloses nucleotide sequences of Aspergillus fumigatus xylanases.
It is an object of the present invention to provide new polypeptides having xylanase activity and nucleic acids encoding the polypeptides.